Explosively actuated mine roof bolt anchor



Nov. 18, 1952 R. TEMPLE EXPLOSIVELY ACTUATED MINE ROOF BOLT ANCHOR FiledFeb. 13, 1951 INVENTOR. Posse?- TEMPL 5.

Patented Nov. 18, 1952 EXPLOSIVELY ACTUATED MINE ROOF BOLT ANCHOR RobertTemple, Swissvale, Pa., assignor to Temple Velocity Equipment, Inc.,Wilmington, DeL, a corporation of Delaware Application February 13,1951, Serial No. 210,637

4 Claims. 1

This invention relates to the bolting of mine roofs to support them, andmore particularly to means for anchoring the upper ends of the bolts inthe bolt holes.

Up until recently, it was the universal practice to support mine roofsby means of timbers. This required horizontal beams and posts forsupporting them. The installation of such timbering is expensive and theposts often take up much-needed space in the mine passages and rooms. Inan efiort to overcome the disadvantages of timbering, the practice isdeveloping in many mines of supporting the roofs by means of bolts whichextend up into holes drilled up into the roofs into the overlying rock.The upper ends of these bolts must be anchored in the rock so that theheads at their lower ends can tightly engage the roof around the lowerends of the holes to support it. The biggest problem in installing suchbolts is to anchor their upper ends in the bolt holes quickly andeffectively. Various ways of doing this have been tried, but heretoforenone of them has been very satisfactory.

It is among the objects of this invention to provide a device foranchoring the upper end of a mine roof bolt in surrounding rock, whichis easy to use, which anchors the bolt very quickly and securely, whichis dependable in operation, and which does not depend on engagement withthe upper end of the roof hole for the anchoring operation.

In accordance with this invention, a vertical barrel-like expansionmember is provided with an axial passage having its lower ortion adaptedto receive and be fastened to the upper end of a bolt, which then is inerted in a hole drilled up into a mine roof. Disposed in the centralportion of the axial passage is an upwardly directed projectile. Theupper portion of the passage is of smaller diameter than the projectile.Means is provided for firing the projectile to drive it upward into therestricted upper portion of the passage in order to expand thesurrounding portion of the expansion member so as to anchor it in thebolt hole. It is preferred that the body of the projectile be formedfrom a hollow stud filled with powder, and that the powder be detonatedby an electric primer inside the stud. The primer can be connected bywires passing out of the stud and the expansion member and down alongthe bolt to a point outside of the bolt hole.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in

' which Fig. 1 is a side view of a bolt and unexpanded anchor insertedin a hole drilled upward from the roof at a mine passage; Fig. 2 is acenvertical section of the anchor; and Fig.3 is a similar verticalsection, but showing the relative positions of the parts of the anchorafter it has been expanded into the surrounding rock.

Referring to Figs. 1 and 2 of the drawings, a hole I is drilled up intothe roof of a mine for several feet. The hole extends up through theshale which is to be supported and into solid rock, such as sandstone,when that is present. A headless bolt 2, threaded at both ends, then isinserted in the hole and its upper end is anchored therein so that thebolt can not be pulled down out of the hole. For anchoring the upper endof the bolt in the surrounding rock 3, an explosive-actuated anchoringdevice is fastened-to its upper end.

In accordance with this invention, the anchor includes a verticalbarrel-like expansion member 5 that has an axial passage 6 extendingthrough it from end to end. The wall of the lower end portion of thispassage is provided with a thread 1 to. permit it to be screwed onto theupper end of the bolt. The upper part of the expansion member preferablyis provided with a plurality of slots 8 extending radially through itand from its upper end downward more or less half-way to the upper endof the bolt. These .slots separate the upper portion of the expansionmember into segments, the outer surfaces of which may be provided withteeth 9 to help them gri the surrounding rock. The diameter of the upperportion of passage 6 is considerably smaller than the diameter of therest of the passage. The large and smaller portions of the passage areconnected by a shoulder l0. Preferably, the small upper portion of thepassage does not extend as far down as the lower ends of slots 8.Consequently, the walls of the segments are thinner at their lower endsthan are their upper portions, which makes bending of them easier,

For expanding the upper portion ofthe expansion member; that is, forcingits segments outward away from one another, a rojectile is disposed inthe central portion of passage 6 between the top of the bolt andshoulder Ill. The body of the projectile is in sliding engagement withthe wall of the passage and preferably is a stud l2 having a taperedupper end and having an axial bore l3 extending upward from its lowerend. The wall of the bore is quite thin. Inside of the bore there is acharge of explosive powder it which is held in the stud by a frictionsealing cap I5 fitted over the lower end of the stud in a shallowannular recess. The cap keeps out moisture and therefore is important incoal mines. 'The powder is exploded preferably by means of an electricprimer I 5 embedded in it at the upper end of the bore [3. Connected tothis primer are the upper ends of wires I! which extend upward out ofthe'stud through an axial opening [8 with which the point of the stud isprovided. The wires then extend out into one of the slots 8 and downthrough a groove I9 in the side of the expansion member extendingdownward from the lower end of the slot. "This groove keeps-the wiresfrom being scraped against the side of the bolt hole. The wires may bewrapped around-the bolt to hold them in the groove and their lower' endsextend out of the bolt hole for connection to a suitable source ofelectricity (not shown), by which the primer head can 'be detonated.

In order to hold down the stud until considerable gas pressure has beenbuilt up by the ex- ;ploding .charge, .and -also .to initially space.the 'studfifromtheloweren'd oftthereduce'cl upper .por- .ition of:apassage CB through Lthe expansion. memy beri so thatLthestud-can gainslittle momentum .ibefore it. strikes lthe .overlying segments,asyieldable ringTZLis. seated around'th'e'itip ofthe stud .inengagementwith shoulder 120. .This' ring-may (be made dfwsoft metalffiberor'thellike, which can momentarilyretard. the projectile but not preventLit .from :moving ahead.

;In .using=this anchor, the lriroject'ile' is inserted in-the expansionmember with ringfZ-i around thepoint o'fLthe stud and with thewiresextend- .ingout'between the segments. The .upper end of-the.boltthen.isscrewed'intolthe lower end of theexpansionmember,which holds'theproj ectile in place withitsupper .end spaced l'from the expansionmember by means of the ring. .The wires .then.can.-.be..pulled. down inthe groove l9 in the .side of -theexpansion member and be wrapped-aroun'd1the boltto holdthem' in the, groove. lBefforeltheanchoreispushed upinto the hole .by meansof =theeboltva .heavy-.plate'22' is slipped up onto the. lower end-of the bolt .and' held .in place'.'.by .a .nut '23. "This ,,.plate serves. as an enlargedjhead-fonthebolt. Thebolt-withtthe anchor at .'its-.upp'er- :end, then.is linserted in the-holeuntil the plateis close to, or. practicallyengages, the roof..of.the.mine. "The. primer wires extend out across theftop..of.the,plate.. "TheLbOlt .may be supported in thispositiondirectly'by 'theioperator or by a temporaryextension (not shown).Screwed .onI'theLboltL belowlthe nut.

:thep'stud up into the. reduced uppenportion, of the ,passage throughJ'the expansion memb'er and ithereby forces the segmentsof that. member.out away 'from one anotheran'd-thus expands the upper. end oftheexpansion member. into the. surrounding rock, as shown in'Fig. 3.'Thepressure 'builds.up very rapidly in the small bore of the :stud, but.untilthe. stud. leaves itscaplthe .pressure hasonlythe smallcross-sectional area of the bore to actagainst to, produce the velocity.of the fstud. .As isoonas the studlleaves 'thecap. 'the high pressuregases expand into passage 6 below the stud, where the diameter of thepassage is as great as the external diameter of the stud. This gives thegases a greatly increased area to act against, thereby giving increasedpower velocity and work to the stud. The gas pressure inside the bore.of thee-stud zexpands its thin wall tightly against the side 10fpassage 6 so that the gas can not escape past the stud, which does notcompletely leave the large lower portion of the passage. Consequently,there is "no escaping gas to'cause noise. Recoil is absent. because thetendency of the explosion to drive .the.-.-.bol-t. downward.iscounteracted by the tend- .ency 10f .thestud to drive the expansionsleeve upward.

The expanded anchor serves as a strong supp'ort'for the bolt that issuspended from it. Following the anchoring operation, which takes only amoment, the nut atthe lower end of the bolt is screwed upward .to .iorceplate L22 tightly .againstthe mine roof to..prevent..the.rcofifrom.Ifalling. Later, ifdes'ired, 'thelbo'lt and plate.'.can be salvagedbyunscrewing the ihlt Qfrom :the

anchor. I

It will be. seen that the anchor -described.herein is of simpleconstruction and'is easy' to .operate. There is nothing .about 'it..togetv out oforder and only a iew'seconds'arerequired .to instalIZita'fter the mine roofi hasbeen drilled. T'It also'.is..rla- .tivelyinexpensiveand requires no movementof the boltto .fire the ,projectile'in .the anchor.

.According to "the .provisions of jthe ,pa'tent statuteslIhave explainedthe -principle of .my invention andhave illustrated andjdescribed what.I now. consider to representits bestemboidiment. However, I 'desire'tohave it gunderstoo'd that,

* within the scope-of the appended claims, .itheinvention may be.practiced otherwiseQthan as rspecifically illustrated. and described.

Lclaim:

1. An explosive-actuated mine roof boltanchor comprisingaverticaltbarrellike expansionmem- 'ber providedwith an. axial passagehaving its lower portion adapted to: receive. and be tastened .totheupper end of -aiboltato' be inserted'ima hole drilled up intoa mine=roof, an.upwardly directed projectile slidabl-y ,mounted.in.the.central-portionof. said passage and having a tapered upper en'd;theupper portionof. the, passagebeing of smallerdiameter' than theprojectileand joined to said central portiontby v ashoulder,.ayi'l'dable retarding ring encircling the. tapered .endof ltheprojectile: and engaging, said :shoulder to .space said tapered .endfromhsaid. member, and. means forjfiring-the projectile to drive itlupwardeinto said upper portion .of the pas age 1-120 eXD- fi hesurrounding ,portion ..of said .member.

. .2. An. explosive-actuated amine ..1:oo"f .cbolt ranchor,.comp'risingra verticallbarrelelike ..expans'ion member provided with anaxial .passa efhaving its lower portion .adapte'dtomeceive.and! belf'as-.tenedto the npperend .of .a" bolt .to .b.e inserted in a hole drilledup intoa mine roof, astuidslidably. mounted in .the central portionzofrsaidpak sage and having an axial .looreextending. upward thereinfrom its lower end,, ,.charge cit-powder Lin-the bore,.removable meansclosing Lthejower end of theibore, an axial. opening .connecting theuppenend of said borewiththetop of-the stud, an electric primerdisposedrin'the. bore, electric wires attached to the primer andextending .up .through said opening, said wires extending out of saidmember. and being. adapted to be-leddown beside it for connection. to.-a. source of electricity outside of said mine roof hole, whereby saidcharge can be detonated electrically to drive the stud upward, the upperportion of said passage being of smaller diameter than the stud so thatwhen the stud is driven upward into it the upper portion of said memberwill be expanded.

3. An explosive-actuated mine roof bolt anchor, comprising a verticalbarrel-like expansion member provided with an axial passage having itslower portion adapted to receive and be fastened. to the upper end of abolt to be inserted 111 a hole drilled up into 53, mine roof, a studslidably mounted in the central portion of said passage and having anaxial bore extending upward therein from its lower end, a charge ofpowder in the bore, removable means closing the lower end of the bore,an axial opening connecting the upper end of said bore with the top ofthe stud, an electric primer disposed in the bore, electric wiresattached to the primer and extending up through said opening, theoutside of said memher being provided with a vertical groove, said wiresextending out of said member and down through said groove, the lowerends of the wires being adapted to be connected to a source ofelectricity outside of said mine roof hole, whereby said charge can bedetonated to drive the stud upward, the upper portion of said passagebeing of smaller diameter than the stud so that when the stud is drivenupward into it the upper portion of said member will be expanded.

4. An explosive-actuated mine roof bolt anchor, comprising a verticalbarrel-like expansion member provided with an axial passage having itslower portion adapted to receive and be fastened to the upper end of abolt to be inserted in a hole drilled up into a mine roof, a stud slidably mounted in the central portion of said passage and having an axialbore extending up ward therein from its lower end, a charge of powder inthe bore, removable means closing the lower end of the bore, the upperend of the stud being tapered, the upper portion of said pass-age beingor" smaller diameter than the projectile and joined to said centralportion by a shoulder, a yieldable retarding ring encircling the taperedend of the stud and engaging said shoulder to space said tapered endfrom said member, and an electric primer in said bore for detonatingsaid charge to drive the stud upward into said upper portion of thepassage to expand the surrounding portion of said member.

ROBERT TEMPLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 750,623 Edmunds Jan. 26, 19042,141,098 Wahlstrom Dec. 20, 1938 2,362,738 Yarbrough Nov. 14, 1944

